Magnetoresistive structures, semiconductor devices, and related systems

ABSTRACT

Magnetic memory cells, methods of fabrication, semiconductor device structures, and memory systems are disclosed. A magnetic cell core includes at least one magnetic region (e.g., a free region or a fixed region) configured to exhibit a vertical magnetic orientation, at least one oxide-based region, which may be a tunnel junction region or an oxide capping region, and at least one magnetic interface region, which may comprise or consist of iron (Fe). In some embodiments, the magnetic interface region is spaced from at least one oxide-based region by a magnetic region. The presence of the magnetic interface region enhances the perpendicular magnetic anisotropy (PMA) strength of the magnetic cell core. In some embodiments, the PMA strength may be enhanced more than 50% compared to that of the same magnetic cell core structure lacking the magnetic interface region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 15/194,875, filed Jun. 28, 2016, now U.S. Pat. No. 9,972,770, issued May 15, 2018, which is a divisional of U.S. patent application Ser. No. 13/797,185, filed Mar. 12, 2013, now U.S. Pat. No. 9,379,315, issued Jun. 28, 2016, the disclosure of each of which is hereby incorporated in its entirety herein by this reference.

TECHNICAL FIELD

The present disclosure, in various embodiments, relates generally to the field of memory device design and fabrication. More particularly, this disclosure relates to design and fabrication of memory cells characterized as spin torque transfer magnetic random access memory (STT-MRAM) cells.

BACKGROUND

Magnetic Random Access Memory (MRAM) is a non-volatile computer memory technology based on magnetoresistance. One type of MRAM cell is a spin torque transfer MRAM (STT-MRAM) cell, which includes a magnetic cell core supported by a substrate. The magnetic cell core includes at least two magnetic regions, for example, a “fixed region” and a “free region,” with a non-magnetic region in-between. The fixed region includes a magnetic material that has a fixed (e.g., a non-switchable) magnetic orientation, while the free region includes a magnetic material that has a magnetic orientation that may be switched, during operation of the cell, between a “parallel” configuration, in which the magnetic orientation of the fixed region and the magnetic orientation of the free region are directed in the same direction (e.g., north and north, east and east, south and south, or west and west, respectively), and an “anti-parallel” configuration, in which the magnetic orientation of the fixed region and the magnetic orientation of the free region are directed in opposite directions (e.g., north and south, east and west, south and north, or west and east, respectively).

In the parallel configuration the STT-MRAM cell exhibits a lower electrical resistance across the magnetoresistive elements, i.e., the fixed region and free region. This state of relatively low electrical resistance may be defined as a “0” state of the MRAM cell. In the anti-parallel configuration, the STT-MRAM cell exhibits a higher electrical resistance across the magnetoresistive elements, i.e., the regions of magnetic material, e.g., the fixed region and free region. This state of relatively high electrical resistance may be defined as a “1” state of the MRAM cell. Switching of the magnetic orientation of the free region and the resulting high or low resistance states across the magnetoresistive elements enables the write and read operations of the conventional MRAM cell. Ideally, the amount of programming current required to switch the free region from the parallel configuration to the anti-parallel configuration is essentially the same amount of programming current required to switch from the anti-parallel configuration to the parallel configuration. Such equal programming current for switching is referred to herein as “symmetric switching.”

The free regions and fixed regions of STT-MRAM cells may exhibit magnetic orientations that are either horizontally oriented (“in-plane”) or perpendicularly oriented (“out-of-plane”) with the width of the regions. In STT-MRAM cells that have perpendicularly-oriented magnetic regions, the magnetic materials exhibiting the vertical magnetic orientation may be characterized by a strength of the magnetic materials' perpendicular magnetic anisotropy (“PMA”). The strength (also referred to herein as the “magnetic strength” or the “PMA strength”) is an indication of the magnetic materials' resistance to alteration of the magnetic orientation. A magnetic material exhibiting a vertical magnetic orientation with a high PMA strength may be less prone to alteration of its magnetic orientation out of the vertical orientation than a magnetic material exhibiting a vertical magnetic orientation with a lower magnetic strength. However, achieving a high PMA strength may not be sufficient, in and of itself, for successful STT-MRAM cell operation. For example, a low resistance-area (RA), a low switching current, a low switching voltage, and symmetric switching may also contribute to successful operation of an STT-MRAM cell. However, finding materials and designs in which a high PMA strength is exhibited without adversely affecting the other characteristics of the STT-MRAM cell's operation, particularly the RA of the cell, may present a challenge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional, elevational, schematic illustration of a magnetic cell core of an STT-MRAM cell including a magnetic interface region disposed directly between a free region and a magnetic tunnel junction region.

FIG. 2 is a cross-sectional, elevational, schematic illustration of a magnetic cell core of an STT-MRAM cell including a magnetic interface region disposed directly between a free region and an oxide cap region.

FIG. 3 is a cross-sectional, elevational, schematic illustration of a magnetic cell core of an STT-MRAM cell including a magnetic interface region disposed directly between a magnetic sub-region of a free region and an oxide cap region.

FIG. 4 is a cross-sectional, elevational, schematic illustration of a magnetic cell core of an STT-MRAM cell including a magnetic interface region disposed within a free region.

FIG. 5 is a cross-sectional, elevational, schematic illustration of a magnetic cell core of an STT-MRAM cell including two magnetic interface regions, one of which being disposed directly between a free region and an oxide cap region and another being disposed directly between the free region and a magnetic tunnel junction region.

FIG. 6 is a cross-sectional, elevational, schematic illustration of a magnetic cell core of an STT-MRAM cell including four magnetic interface regions, of which one pair is disposed on top and on bottom of a free region and another pair is disposed on top and on bottom of a fixed region.

FIG. 7 is a cross-sectional, elevational, schematic illustration of a magnetic cell core of an STT-MRAM cell including one magnetic interface region within a free region and another magnetic interface region on top of a fixed region.

FIG. 8 is a schematic diagram of an STT-MRAM system having a memory cell according to an embodiment of the present disclosure.

FIG. 9 is a simplified block diagram of a semiconductor device structure including memory cells of an embodiment of the present disclosure.

FIG. 10 is a simplified block diagram of a system implemented according to one or more embodiments of the present disclosure.

FIG. 11 is a graph displaying measurements of PMA strength for a magnetic cell core incorporating a magnetic interface region in comparison with a magnetic cell core lacking the magnetic interface region.

DETAILED DESCRIPTION

Memory cells, semiconductor device structures including such memory cells, memory systems, and methods of forming such memory cells are disclosed. The memory cells include a magnetic region, such as a free region or a fixed region, exhibiting a vertical magnetic orientation. The memory cells also include at least one oxide region, such one or more of an oxide-based magnetic tunnel junction (“MTJ”) region and an oxide capping region. Disposed, directly or indirectly, between the magnetic region and the oxide region is a magnetic interface region that is configured to increase the PMA strength of the memory cell, compared to memory cells lacking the magnetic interface region, but without significantly adversely affecting other characteristics of the memory cell, such as the resistance-area of the memory cell. For example, a low RA (e.g., less than about 20 Ω·μm² (Ohms×microns squared)) may be maintained even with enhanced PMA strength (e.g., a uniaxial anisotropy field (H_(k)) exceeding about 4,000 Oe (Oersted)). Accordingly, the magnetic interface region may enhance operational performance of the magnetic region (e.g., the free region or the fixed region) within a magnetic memory cell structure that accommodates high data retention time and low power operation.

As used herein, the term “substrate” means and includes a base material or other construction upon which components, such as those within memory cells, are formed. The substrate may be a semiconductor substrate, a base semiconductor material on a supporting structure, a metal electrode, or a semiconductor substrate having one or more materials, structures, or regions formed thereon. The substrate may be a conventional silicon substrate or other bulk substrate including a semiconductive material. As used herein, the term “bulk substrate” means and includes not only silicon wafers, but also silicon-on-insulator (“SOI”) substrates, such as silicon-on-sapphire (“SOS”) substrates or silicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on a base semiconductor foundation, or other semiconductor or optoelectronic materials, such as silicon-germanium (Si_(1-x)Ge_(x), where x is, for example, a mole fraction between 0.2 and 0.8), germanium (Ge), gallium arsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP), among others. Furthermore, when reference is made to a “substrate” in the following description, previous process stages may have been utilized to form materials, regions, or junctions in the base semiconductor structure or foundation.

As used herein, the term “STT-MRAM cell” means and includes a magnetic cell structure that includes a non-magnetic region disposed between a free region and a fixed region. The non-magnetic region may be an electrically insulative (e.g., dielectric) region, in a magnetic tunnel junction (“MTJ”) configuration. Alternatively, the non-magnetic region may be an electrically conductive region, in a spin-valve configuration.

As used herein, the term “cell core” means and includes a memory cell structure comprising the free region and fixed region and through which, during use and operation of the memory cell, current flows to effect a parallel or anti-parallel magnetic orientation within the free region.

As used herein, the term “vertical” means and includes a direction that is perpendicular to the width and length of the respective region. “Vertical” may also mean and include a direction that is perpendicular to a primary surface of the substrate on which the STT-MRAM cell is located.

As used herein, the term “horizontal” means and includes a direction that is parallel to at least one of the width and length of the respective region. “Horizontal” may also mean and include a direction that is parallel to a primary surface of the substrate on which the STT-MRAM cell is located.

As used herein, the term “magnetic material” means and includes ferromagnetic materials, ferrimagnetic materials, and antiferromagnetic materials.

As used herein, the term “iron-based material” means and includes a material that includes iron. For example, and without limitation, iron-based materials include pure iron, an iron alloy, and materials including cobalt and iron. The composition of the iron-based material may be altered due to annealing of the iron-based material during fabrication of the magnetic memory cell, but such material may, nonetheless, be referred to herein as an “iron-based material.”

As used herein, the term “magnetic region” means a region that exhibits magnetism. A magnetic region includes a magnetic material and may also include one or more non-magnetic materials.

As used herein, the term “sub-region,” means and includes a region included in another region. Thus, one magnetic region may include one or more magnetic sub-regions, i.e., sub-regions of magnetic material, as well as non-magnetic sub-regions, i.e., sub-regions of non-magnetic material.

As used herein, the term “fixed region” means and includes a magnetic region within the STT-MRAM cell that includes magnetic material and that has a fixed magnetic orientation during use and operation of the STT-MRAM cell in that a current or applied field effecting a change in the magnetization direction of one magnetic region, e.g., the free region, of the cell core may not effect a change in the magnetization direction of the fixed region. The fixed region may include one or more magnetic materials and, optionally, one or more non-magnetic materials. For example, the fixed region may be configured as a synthetic antiferromagnet (SAF) including a sub-region of ruthenium (Ru) adjoined by magnetic sub-regions. Each of the magnetic sub-regions may include one or more materials and one or more regions therein. As another example, the fixed region may be configured as a single, homogenous magnetic material. Accordingly, the fixed region may have uniform magnetization or sub-regions of differing magnetization that, overall, effect the fixed region having a fixed magnetic orientation during use and operation of the STT-MRAM cell.

As used herein, the term “free region” means and includes a magnetic region within the STT-MRAM cell that includes magnetic material and that has a switchable magnetic orientation during use and operation of the STT-MRAM cell. The magnetic orientation may be switched between a “parallel” direction, in which the magnetic orientation exhibited by the free region and the magnetic orientation exhibited by the fixed region are oriented in the same direction, and an “anti-parallel” direction, in which the magnetic orientation exhibited by the free region and the magnetic orientation exhibited by the fixed region are oriented in opposite directions from one another.

As used herein, the term “oxide region” means and includes a region within the STT-MRAM cell that includes an oxide material. For example, and without limitation, an oxide region may include an oxide-based MTJ region, an oxide capping region, or both.

As used herein, the term “between” is a spatially relative term used to describe the relative disposition of one material, region, or sub-region relative to at least two other materials, regions, or sub-regions. The term “between” can encompass both a disposition of one material, region, or sub-region directly adjacent to the other materials, regions, or sub-regions and a disposition of one material, region, or sub-region not directly adjacent to the other materials, regions, or sub-regions.

As used herein, reference to an element as being “on” or “over” another element means and includes the element being directly on top of, adjacent to, underneath, or in direct contact with the other element. It also includes the element being indirectly on top of, adjacent to, underneath, or near the other element, with other elements present therebetween. In contrast, when an element is referred to as being “directly on” or “directly adjacent to” another element, there are no intervening elements present.

As used herein, other spatially relative terms, such as “beneath,” “below,” “lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,” “right,” and the like, may be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation as depicted in the figures. For example, if materials in the figures are inverted, elements described as “below” or “beneath” or “under” or “on bottom of” other elements or features would then be oriented “above” or “on top of” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below, depending on the context in which the term is used, which will be evident to one of ordinary skill in the art. The materials may be otherwise oriented (rotated 90 degrees, inverted, etc.) and the spatially relative descriptors used herein interpreted accordingly.

As used herein, the terms “comprises,” “comprising,” “includes,” and/or “including” specify the presence of stated features, regions, integers, stages, operations, elements, materials, components, and/or groups, but do not preclude the presence or addition of one or more other features, regions, integers, stages, operations, elements, materials, components, and/or groups thereof.

As used herein, “and/or” includes any and all combinations of one or more of the associated listed items.

As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The illustrations presented herein are not meant to be actual views of any particular component, structure, device, or system, but are merely idealized representations that are employed to describe embodiments of the present disclosure.

Embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations. Accordingly, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein are not to be construed as limited to the particular shapes or regions as illustrated, but include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as box-shaped may have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the materials, features, and regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of a material, feature, or region and do not limit the scope of the present claims.

The following description provides specific details, such as material types and processing conditions, in order to provide a thorough description of embodiments of the disclosed devices and methods. However, a person of ordinary skill in the art will understand that the embodiments of the devices and methods may be practiced without employing these specific details. Indeed, the embodiments of the devices and methods may be practiced in conjunction with conventional semiconductor fabrication techniques employed in the industry.

The fabrication processes described herein do not form a complete process flow for processing semiconductor device structures. The remainder of the process flow is known to those of ordinary skill in the art. Accordingly, only the methods and semiconductor device structures necessary to understand embodiments of the present devices and methods are described herein.

Unless the context indicates otherwise, the materials described herein may be formed by any suitable technique including, but not limited to, spin coating, blanket coating, chemical vapor deposition (“CVD”), atomic layer deposition (“ALD”), plasma enhanced ALD, or physical vapor deposition (“PVD”). Alternatively, the materials may be grown in situ. Depending on the specific material to be formed, the technique for depositing or growing the material may be selected by a person of ordinary skill in the art.

Unless the context indicates otherwise, the removal of materials described herein may be accomplished by any suitable technique including, but not limited to, etching, ion milling, abrasive planarization, or other known methods.

Reference will now be made to the drawings, where like numerals refer to like components throughout. The drawings are not necessarily drawn to scale.

A memory cell is disclosed. The memory cell includes at least one magnetic region (e.g., a free region or a fixed region) exhibiting a vertical magnetic orientation and an oxide region (e.g., an MTJ region or an oxide capping region) with a magnetic interface region disposed, directly or indirectly, therebetween. The magnetic interface region may enhance the PMA strength of the magnetic memory cell. The magnetic interface region may be disposed adjacent to or within its respective magnetic region. In some embodiments, the memory cell may include only one magnetic interface region; however, in other embodiments, more than one magnetic interface region may be included in the memory cell.

FIG. 1 illustrates a magnetic cell core 100 of an STT-MRAM cell according to an embodiment of the present disclosure. The magnetic cell core 100 is supported by a substrate 102. The magnetic cell core 100 includes at least two magnetic regions, for example, a “fixed region” 110 and a “free region” 120 with a nonmagnetic region 130 in between. One or more lower intermediary regions 140 and one or more upper intermediary regions 150 may, optionally, be disposed under and over, respectively, the magnetic regions (e.g., the fixed region 110 and the free region 120) of the magnetic cell core 100 structure.

In some embodiments, as illustrated in FIG. 1, the magnetic cell core 100 may include an optional conductive material forming a seed region 160 on the substrate 102. The seed region 160, if present, or the lower intermediary regions 140, if the seed region 160 is not present, may be formed over a bottom conductive material (not shown), which may include, for example and without limitation, copper, tungsten, titanium, or a combination thereof. The seed region 160, if present, may include, for example and without limitation, a nickel-based material and may be configured to control the crystal structure of an overlying material or region. The lower intermediary regions 140, if present, may include materials configured to ensure a desired crystal structure of overlying materials in the magnetic cell core 100.

The STT-MRAM cell may be configured to exhibit a vertical magnetic orientation in at least one of the magnetic regions (e.g., the fixed region 110 and the free region 120). The vertical magnetic orientation exhibited may be characterized by the perpendicular magnetic anisotropy (“PMA”) strength. As illustrated in FIG. 1 by arrows 112 and 122, in some embodiments, each of the fixed region 110 and the free region 120 may exhibit a vertical magnetic orientation. The magnetic orientation of the fixed region 110 may remain directed in essentially the same direction throughout operation of the STT-MRAM cell, for example, in the direction indicated by arrows 112 of FIG. 1. The magnetic orientation of the free region 120, on the other hand, may be switched, during operation of the cell, between a “parallel” configuration and an “anti-parallel” configuration, as indicated by double-pointed arrows 122 of FIG. 1. In the parallel orientation, the magnetic orientation 122 of the free region 120 is directed in essentially the same direction (e.g., north) as the magnetic orientation 112 of the fixed region 110 (e.g., north), producing a lower electrical resistance across the magnetoresistive elements, i.e., the fixed region 110 and the free region 120, in what may be defined as the “0” state of the STT-MRAM cell. In the anti-parallel configuration, the magnetic orientation 122 of the free region 120 is directed essentially in the opposite direction (e.g., south) of the magnetic orientation 112 of the fixed region 110 (e.g. north), producing a higher electrical resistance across the magnetoresistive elements, i.e., the fixed region 110 and the free region 120, in what may be defined as the “1” state of the STT-MRAM cell.

In use and operation, a programming current may be caused to flow through an access transistor (not shown) and the magnetic cell core 100. The fixed region 110 within the magnetic cell core 100 polarizes the electron spin of the programming current. The spin-polarized electron current interacts with the free region 120 by exerting a torque on the free region 120. When the torque of the spin-polarized electron current passing through the free region 120 is greater than a critical switching current density (J_(c)) of the free region 120, the torque exerted by the spin-polarized electron current is sufficient to switch the direction of the magnetization of the free region 120, e.g., between a north-directed magnetic orientation and a south-directed magnetic orientation. Thus, the programming current can be used to cause the magnetic orientation 122 of the free region 120 to be aligned either parallel to or anti-parallel to the magnetic orientation 112 of the fixed region 110.

The free region 120 and the fixed region 110 may be formed from or comprise ferromagnetic materials, such as Co, Fe, Ni, or their alloys, NiFe, CoFe, CoNiFe, or doped alloys CoX, CoFeX, CoNiFeX (X═B, Cu, Re, Ru, Rh, Hf, Pd, Pt, C), or other half-metallic ferromagnetic materials, such as, for example, NiMnSb and PtMnSb. In some embodiments, for example, the free region 120, the fixed region 110, or both may be formed from Co_(x)Fe_(y)B_(z), wherein x=10 to 80, y=10 to 80, and z=0 to 50. In other embodiments, the free region 120, the fixed region 110, or both may be formed of iron (Fe) and boron (B) and not include cobalt (Co). The compositions and structures (e.g., the thicknesses and other physical dimensions) of the free region 120 and the fixed region 110 may be the same or different.

Alternatively or additionally, in some embodiments, the free region 120, the fixed region 110, or both, may be formed from or comprise a plurality of materials, some of which may be magnetic materials and some of which may be nonmagnetic materials. For example, some such multi-material free regions, fixed regions, or both, may include multiple sub-regions. For example, and without limitation, the free region 120, the fixed region 110, or both, may be formed from or comprise repeating sub-regions of cobalt and platinum, wherein a sub-region of platinum may be disposed between sub-regions of cobalt. As another example, without limitation, the free region 120, the fixed region 110, or both, may comprise repeating sub-regions of cobalt and nickel, wherein a sub-region of nickel may be disposed between sub-regions of cobalt.

The nonmagnetic region 130, disposed between the fixed region 110 and the free region 120, may include nonmagnetic materials (such as a nonmagnetic oxide material, e.g., magnesium oxide (MgO), aluminum oxide (Al₂O₃), titanium oxide (TiO₂), or other oxide materials of conventional MTJ regions). Accordingly, such oxide-including MTJ region may be referred to herein as an “oxide-based MTJ region” or an “oxide-based nonmagnetic region.” The nonmagnetic region 130 may include one or more such nonmagnetic materials. Alternatively or additionally, the nonmagnetic region 130 may include sub-regions of one or more nonmagnetic materials.

As illustrated in FIG. 1, the magnetic cell core 100 may, in some embodiments, include an oxide capping region 170, which may include oxides such as MgO, TiO₂, tantalum pentoxide (Ta₂O₅), or combinations thereof. Accordingly, such oxide-including capping region may be referred to herein, also, as an “oxide-based nonmagnetic region.” In some embodiments, the oxide capping region 170 may include the same materials, structure, or both of the nonmagnetic region 130. For example, the oxide capping region 170 and the nonmagnetic region 130 may both include a magnesium oxide (e.g., MgO), an aluminum oxide, a titanium oxide, a zinc oxide, hafnium oxide, a ruthenium oxide, or a tantalum oxide.

The optional upper intermediary regions 150, if present, may include materials configured to ensure a desired crystal structure in neighboring materials of the magnetic cell core 100. The upper intermediary regions 150 may alternatively or additionally include metal materials configured to aid in patterning processes during fabrication of the magnetic cell core 100, barrier materials, or other materials of conventional STT-MRAM cell core structures. In some embodiments, such as that illustrated in FIG. 1, the upper intermediary regions 150 may include a conductive capping region, which may include one or more materials such as copper, tantalum, titanium, tungsten, ruthenium, tantalum nitride, or titanium nitride.

The magnetic cell core 100, according to the present disclosure, also includes a magnetic interface region 180 disposed between one of the magnetic regions or magnetic sub-regions (e.g., the fixed region 110, a magnetic sub-region of the fixed region 110, the free region 120, or a magnetic sub-region of the free region 120) and one of the oxide regions (e.g., the nonmagnetic region 130 and the oxide capping region 170). As illustrated in FIG. 1, the magnetic interface region 180 may be disposed directly adjacent to one of the magnetic regions or magnetic sub-regions and one of the oxide regions. According to the embodiment illustrated in FIG. 1, the magnetic interface region 180 may be disposed directly on top of the nonmagnetic region 130 and directly beneath the free region 120. As situated, the magnetic interface region 180 may be disposed between two oxide regions, i.e., between an oxide-based MTJ (e.g., the nonmagnetic region 130) and the oxide capping region 170.

The magnetic interface region 180 may be configured to enhance the PMA strength of the magnetic cell core 100, or, more particularly, of its neighboring magnetic region, e.g., the free region 120 according to the embodiment illustrated in FIG. 1. The increased PMA may be achieved while maintaining a low resistance-area (e.g., less than about 20 Ω·μm² (Ohms×microns squared)) of the magnetic cell core 100. The magnetic interface region 180 may be formed of a magnetic material, such as an iron-based material, e.g., iron (Fe) alone, an iron alloy, or, in some embodiments, a cobalt-iron (CoFe) based material.

The material of the magnetic interface region 180 may be in the form of a monolayer of iron or other iron-including compound disposed between the nonmagnetic region 130 and the oxide capping region 170. Alternatively or additionally, the magnetic interface region 180 may have a thickness (i.e., a height along an axis perpendicular to an upper surface of the substrate 102) that is less than about 10 Å (e.g., less than about 5 Å, e.g., about 3 Å). As such, the magnetic interface region 180 may be thinner than its neighboring regions. For example, the overlying free region 120 of FIG. 1 may be formed to have a thickness of about 15 Å to about 30 Å, and the underlying nonmagnetic region 130 of FIG. 1 may be formed to have a thickness of about 7 Å to about 10 Å.

The magnetic interface region 180 may be formed from a material formulated or otherwise configured to have the same crystal orientation as that of the material upon which it is formed. For example, according to the embodiment illustrated in FIG. 1, the magnetic interface region 180 may be formed from iron (Fe) in such a manner (e.g., by magnetron sputtering) as to have the same crystal orientation as MgO within the nonmagnetic region 130.

The magnetic interface region 180 may be formed by, e.g., magnetron sputtering. For example, the materials of the lower regions of the magnetic cell core 100 may be formed successively, such as in layers, following which the magnetic material of the magnetic interface region 180 may be formed over the previously-formed materials. The materials of the upper regions of the magnetic cell core 100 may then be formed successively, such as in layers, above the magnetic material of the magnetic interface region 180. Accordingly, the material of the magnetic interface region 180 may be formed so as to be disposed between two oxide-based materials, i.e., the oxide materials from which the nonmagnetic region 130 and the oxide capping region 170 are to be formed.

Following formation of the materials of the magnetic cell core 100, the materials may be patterned to form the magnetic cell core 100 comprising the various regions thereof. Techniques for forming and patterning the materials of the lower and upper regions of the magnetic cell core 100 are known in the art and, therefore, are not described in detail herein. For example, the magnetic cell core 100 may be formed by forming each of the materials of the regions thereof in sequential order, from base to top, and then patterning the materials to define the magnetic cell core 100. The magnetic cell core 100 structure may be annealed at a temperature of at least 150° C. (e.g., between about 150° C. and about 400° C.) before or after patterning. Alternatively or additionally, materials of the magnetic cell core 100 structure may be annealed during fabrication of the magnetic cell core 100 structure, e.g., after formation of one or more materials of the magnetic cell core 100 structure and before other materials thereof are formed.

In embodiments such as that illustrated in FIG. 1, in which the magnetic interface region 180 is disposed directly between the nonmagnetic region 130 and the free region 120, and in which the magnetic interface region 180 is disposed between the nonmagnetic region 130 and the oxide capping region 170, it is contemplated that, without being bound to any one particular theory, the magnetic interface region 180 enables iron-oxygen bonding between iron in the magnetic interface region 180 and oxygen in the oxide material of the neighboring oxide-based region, e.g., the nonmagnetic region 130. Iron-oxygen bonding may contribute to interfacial PMA strength. It is contemplated that the contribution to interfacial PMA strength by iron-oxygen bonding may be greater than a contribution from other oxygen bonding, such as cobalt-oxygen bonding. Accordingly, the inclusion of the magnetic interface region 180 in the magnetic cell core 100 may enable a stronger PMA than that achieved by a magnetic cell core structure lacking a magnetic interface region 180 between a magnetic region such as the free region 120 and an oxide region such as the nonmagnetic region 130.

Accordingly, disclosed is a memory cell comprising a magnetic cell core on a substrate. The magnetic cell core comprises a magnetic region between an oxide region and another oxide region. The magnetic region exhibits a vertical magnetic orientation. A magnetic interface region is disposed between the oxide region and the another oxide region.

With reference to FIG. 2, illustrated is a magnetic cell core 200 in which the magnetic interface region 180 is disposed between the nonmagnetic region 130 and the oxide capping region 170, but above the free region 120. Thus, the nonmagnetic region 130 is disposed to one side of, e.g., underneath, the free region 120 while the magnetic interface region 180 is disposed to another side of, e.g., above, the free region 120. The materials of the magnetic cell core 200 may be the same as those of the magnetic cell core 100 (FIG. 1) described above. The magnetic cell core 200 may be formed by forming each of the materials of the regions thereof in sequential order, from base to top, and then patterning the materials to define the magnetic cell core 200 structure. Thus, the magnetic interface region 180 may be formed directly on the free region 120, and the oxide capping region 170 may be formed directly on the magnetic interface region 180. In other embodiments (not shown in FIG. 2), the positions of the free region 120 and the fixed region 110 may be interchanged such that the magnetic interface region 180 would be disposed between the oxide capping region 170 and the fixed region 110, which would be positioned above the nonmagnetic region 130.

Accordingly, disclosed is a method of forming a memory cell, the method comprising forming an oxide material over a substrate. A magnetic material is formed over the oxide material. Another oxide material is formed over the magnetic material. An iron-based material is formed between the magnetic material and one of the oxide material and the another oxide material. The oxide material, the magnetic material, the another oxide material, and the iron-based material are patterned to form a magnetic cell core comprising a tunnel junction region from the oxide material, one of a free region and a fixed region from the magnetic material, a magnetic interface region from the iron-based material, and an oxide capping region from the another oxide material. The magnetic material exhibits a vertical magnetic orientation.

With reference to FIG. 3, in some embodiments, a magnetic cell core 300 according to the present disclosure may include magnetic regions, such as the free region, the fixed region, or both, having a multi-material structure. For example, the fixed region 110 of the embodiment of FIG. 3, or any of the preceding or following described embodiments, may be configured as an SAF with a Ru sub-region neighbored on top and bottom by a magnetic sub-region. As another example, as illustrated, the magnetic cell core 300 may include a multi-material free region 320. The multi-material free region 320 may include an upper magnetic sub-region 324 spaced from (i.e., not directly in physical contact with) a lower magnetic sub-region 326 by a spacer 328. In other embodiments, the multi-material free region 320 may lack the spacer 328. In still other embodiments, the multi-material free region 320 may have more than two magnetic sub-regions, more than one spacer 328, or both.

The material or materials from which the upper magnetic sub-region 324 and the lower magnetic sub-region 326 are formed may be the same material or materials, respectively, from which the free region 120 may be formed, as described above. For example, and without limitation, each of the upper magnetic sub-region 324 and the lower magnetic sub-region 326 may be formed from Co_(x)Fe_(y)B_(z), wherein x=1, y=50 to 60, and z=1 to 30, e.g., CoFe₅₀B₃₀. As another example, the upper magnetic sub-region 324 may be formed of CoFeB₆₀ while the lower magnetic sub-region 326 may be formed of CoFe₅₀B₃₀.

Each of the upper magnetic sub-region 324 and the lower magnetic sub-region 326 may be formed to each be thicker than the spacer 328. In some embodiments, the lower magnetic sub-region 326 may have a thickness of about 10 Å, and the upper magnetic sub-region 324 may have a thickness of about 6 Å. In other embodiments, the upper magnetic sub-region 324 and the lower magnetic sub-region 326 may be formed to have approximately equal thicknesses, e.g., from about 6 Å to about 10 Å.

The spacer 328 may be formed from a conductive material such as, for example and without limitation, tantalum (Ta). The spacer 328 may be relatively thin compared to the overlying and underlying sub-regions. For example, the spacer 328 may have a thickness of less than about 3 Å, e.g., about 1.5 Å.

The multi-material free region 320 may be formed by forming each of the materials thereof sequentially, from base to top, before the materials are patterned to form the magnetic cell core 300.

According to the embodiment of FIG. 3, the magnetic interface region 180 may be formed over the multi-material free region 320, so as to be disposed between the nonmagnetic region 130 and the oxide capping region 170. Thus, the magnetic interface region 180 may be directly between the upper magnetic sub-region 324 and the oxide capping region 170.

Accordingly, disclosed is a memory cell comprising a magnetic cell core comprising a free region configured to exhibit a switchable vertical magnetic orientation and a fixed region configured to exhibit a fixed vertical magnetic orientation. A nonmagnetic region is disposed between the free region and the fixed region. A magnetic interface region is spaced from the nonmagnetic region by one of the free region and the fixed region.

With reference to FIG. 4, a magnetic cell core 400, according to the present disclosure, having a multi-material free region 420 comprising the upper magnetic sub-region 324, the lower magnetic sub-region 326, and the spacer 328, may be structured to also comprise the magnetic interface region 180. That is, the magnetic interface region 180 may be disposed directly adjacent to, either above or below, the spacer 328 and one of the upper magnetic sub-region 324 and the lower magnetic sub-region 326. In this structure, the magnetic interface region 180 is spaced from both of the oxide-based regions, i.e., the nonmagnetic region 130 and the oxide capping region 170. Nonetheless, the presence of the magnetic interface region 180 may enhance the PMA strength of at least the magnetic region incorporating the magnetic interface region 180, which, as illustrated in in FIG. 4, may be the free region (e.g., the multi-material free region 420). For example, the PMA strength of the magnetic region (e.g., the multi-material free region 420) may be greater than about 4,000 Oersted (e.g., greater than about 5,000 Oersted).

In a structure such as that of the magnetic cell core 400 of FIG. 4, the upper magnetic sub-region 324 and the lower magnetic sub-region 326 may be of the same thicknesses. Alternatively, the total thickness of the magnetic interface region 180 and the one of the upper magnetic sub-region 324 and the lower magnetic sub-region 326 to which the magnetic interface region 180 is adjacent may be about equal to the thickness of the other of the upper magnetic sub-region 324 and the lower magnetic sub-region 326. For example, the lower magnetic sub-region 326 may have a thickness of about 10 Å, while the upper magnetic sub-region 324 may have a thickness of about 6 Å and the magnetic interface region 180 may have a thickness of about 4 Å.

The materials of the multi-material free region 420 may be formed sequentially, from base to top, whereby the magnetic interface region 180 may be formed directly on the spacer 328, and the upper magnetic sub-region 324 may be formed directly on the magnetic interface region 180.

With reference to FIG. 5, a magnetic cell core 500 according to the present disclosure may, alternatively, include more than one magnetic interface region 180. For example, as illustrated in FIG. 5, a pair of magnetic interface regions 180 may be disposed such that one overlies one of the magnetic regions of the magnetic cell core 500, e.g., overlies the free region 120, while another magnetic interface region 180 of the pair underlies the same magnetic region, e.g., underlies the free region 120. Again, the materials of the magnetic cell core 500 may be formed sequentially, from base to top, and may be patterned to form the magnetic cell core 500.

With reference to FIG. 6, in some embodiments a magnetic cell core 600 may include more than two magnetic interface regions 180, such as one magnetic interface region 180 directly on each of the top and bottom of each of the magnetic regions (e.g., the free region 120 and the fixed region 110) of the magnetic cell core 600. Again, the materials of the magnetic cell core 600 may be formed sequentially, from base to top, and may be thereafter patterned to form the magnetic cell core 600.

With reference to FIG. 7, it is contemplated that one of the magnetic regions of a magnetic cell core 700, such as the free region or, for example, a multi-material free region 720 may incorporate the magnetic interface region 180 while another magnetic region of the magnetic cell core 700, such as the fixed region 110 may be adjacent to another magnetic interface region 180. Again, the materials of such magnetic cell core 700 may be formed sequentially, from base to top.

Accordingly, the number of magnetic interface regions 180 and the disposition of such magnetic interface regions 180 may be tailored according to the desired STT-MRAM structure and operability. Likewise, the exact composition and thickness of the magnetic interface region 180 may be tailored to achieve a desired PMA strength, which may be the highest PMA strength (e.g., H_(k) (Oe)) achievable without adversely impacting the operation of the STT-MRAM cell. It is contemplated that the thickness of the magnetic interface region 180 may be optimized, through testing, to be of a thickness great enough to enhance the PMA strength while less than the thickness that would negatively impact the operation characteristics of the STT-MRAM cell.

In embodiments in which multiple magnetic interface regions 180 are included in the magnetic cell core (e.g., magnetic cell cores 500, 600, or 700), the magnetic interface regions 180 within the magnetic cell cores 500, 600, or 700 may have equal thicknesses or, alternatively, the thicknesses of the magnetic interface regions 180 may vary from one another. Again, it is contemplated that the relative thicknesses of the multiple magnetic interface regions 180 may be optimized, through testing.

Following formation of the magnetic cell core (e.g., one of magnetic cell cores 100-700), the semiconductor device structure may be subjected to additional fabrication steps, as known in the art, to form an operational semiconductor device, such as an STT-MRAM cell, an array of STT-MRAM cells, an STT-MRAM system, a processor-based system, or any combination thereof.

With reference to FIG. 8, illustrated is an STT-MRAM system 800 that includes peripheral devices 812 in operable communication with an STT-MRAM cell 814, a plurality of which may be fabricated to form an array of memory cells in a grid pattern including a number of rows and columns, or in various other arrangements, depending on the system requirements and fabrication technology. The STT-MRAM cell 814 includes a cell core 802, an access transistor 803, a conductive material that may function as a data/sense line 804 (e.g., a bit line), a conductive material that may function as an access line 805 (e.g., a word line), and a conductive material that may function as a source line 806. The peripheral devices 812 of the STT-MRAM system 800 may include read/write circuitry 807, a bit line reference 808, and a sense amplifier 809. The cell core 802 may be any one of the magnetic cell cores 100-700 described above. Due to the structure of the cell core 802, i.e., the inclusion of the magnetic interface region 180 (FIGS. 1-7) that is spaced from the nonmagnetic region 130, e.g., the tunnel region or MTJ, or from the oxide capping region 170 and the resultant enhancement of the PMA strength of the STT-MRAM cell 814, the STT-MRAM cell 814 may exhibit a higher data retention time and operate effectively at lower power than a conventional STT-MRAM cell.

In use and operation, when an STT-MRAM cell 814 is selected to be programmed, a programming current is applied to the STT-MRAM cell 814, and the current is spin-polarized by the fixed region of the cell core 802 and exerts a torque on the free region of the cell core 802, which switches the magnetization of the free region to “write to” or “program” the STT-MRAM cell 814. In a read operation of the STT-MRAM cell 814, a current is used to detect the resistance state of the cell core 802.

To initiate programming of the STT-MRAM cell 814, the read/write circuitry 807 may generate a write current to the data/sense line 804 and the source line 806. The polarity of the voltage between the data/sense line 804 and the source line 806 determines the switch in magnetic orientation of the free region in the cell core 802. By changing the magnetic orientation of the free region with the spin polarity, the free region is magnetized according to the spin polarity of the programming current, the programmed state is written to the STT-MRAM cell 814.

To read the STT-MRAM cell 814, the read/write circuitry 807 generates a read voltage to the data/sense line 804 and the source line 806 through the cell core 802 and the access transistor 803. The programmed state of the STT-MRAM cell 814 relates to the resistance across the cell core 802, which may be determined by the voltage difference between the data/sense line 804 and the source line 806. In some embodiments, the voltage difference may be compared to the bit line reference 808 and amplified by the sense amplifier 809.

FIG. 8 illustrates one example of an operable STT-MRAM system 800. It is contemplated, however, that the magnetic cell cores 100-700 (FIGS. 1-7) may be incorporated and utilized within any STT-MRAM system configured to incorporate a magnetic cell core having magnetic regions exhibiting vertical magnetic orientations. Notably, because the thickness of the magnetic interface region 180 (FIGS. 1-7) may be relatively thin, relative to other regions of the magnetic cell cores 100-700, the total height of the magnetic cell cores 100-700 may be the same or not much greater than the height of a conventional magnetic cell core of an STT-MRAM cell. Further, because the magnetic interface region 180 may be formed using techniques the same as or similar to techniques used to form other regions of the magnetic cell cores 100-700, the overall fabrication process may not be significantly altered to accomplish formation of the magnetic cell cores 100-700 in accordance with embodiments of the present disclosure.

Accordingly, disclosed is a spin torque transfer magnetic random access memory (STT-MRAM) system comprising a magnetic cell core comprising a magnetic interface region on or in a magnetic region. The magnetic region is configured to exhibit a vertical magnetic orientation. An oxide region is spaced from the magnetic interface region. The STT-MRAM system also comprises a plurality of conductive materials in operable communication with the magnetic cell core.

With reference to FIG. 9, illustrated is a simplified block diagram of a semiconductor device structure 900 implemented according to one or more embodiments described herein. The semiconductor device structure 900 includes a memory array 902 and a control logic component 904. The memory array 902 may include a plurality of the STT-MRAM cells 814 (FIG. 8) including any of the magnetic cell cores 100-700 (FIGS. 1-7) discussed above, which magnetic cell cores 100-700 (FIGS. 1-7) may have been formed according to a method described above. The control logic component 904 may be configured to operatively interact with the memory array 902 so as to read from or write to any or all memory cells (e.g., STT-MRAM cell 814) within the memory array 902.

Accordingly, disclosed is a semiconductor device structure comprising a spin torque transfer magnetic random access memory (STT-MRAM) array comprising a plurality of STT-MRAM cells. Each STT-MRAM cell of the plurality comprises a cell core comprising a nonmagnetic region between a magnetic region and another magnetic region. Each of the magnetic region and the another magnetic region are configured to exhibit a vertical magnetic orientation. An oxide region is spaced from the nonmagnetic region by one of the magnetic region and the another magnetic region. A magnetic interface region is disposed between the oxide region and the nonmagnetic region.

With reference to FIG. 10, depicted is a processor-based system 1000. The processor-based system 1000 may include various electronic devices manufactured in accordance with embodiments of the present disclosure. The processor-based system 1000 may be any of a variety of types such as a computer, pager, cellular phone, personal organizer, control circuit, or other electronic device. The processor-based system 1000 may include one or more processors 1002, such as a microprocessor, to control the processing of system functions and requests in the processor-based system 1000. The processor 1002 and other subcomponents of the processor-based system 1000 may include magnetic memory devices manufactured in accordance with embodiments of the present disclosure.

The processor-based system 1000 may include a power supply 1004. For example, if the processor-based system 1000 is a portable system, the power supply 1004 may include one or more of a fuel cell, a power scavenging device, permanent batteries, replaceable batteries, and rechargeable batteries. The power supply 1004 may also include an AC adapter; therefore, the processor-based system 1000 may be plugged into a wall outlet, for example. The power supply 1004 may also include a DC adapter such that the processor-based system 1000 may be plugged into a vehicle cigarette lighter or a vehicle power port, for example.

Various other devices may be coupled to the processor 1002 depending on the functions that the processor-based system 1000 performs. For example, a user interface 1006 may be coupled to the processor 1002. The user interface 1006 may include input devices such as buttons, switches, a keyboard, a light pen, a mouse, a digitizer and stylus, a touch screen, a voice recognition system, a microphone, or a combination thereof. A display 1008 may also be coupled to the processor 1002. The display 1008 may include an LCD display, an SED display, a CRT display, a DLP display, a plasma display, an OLED display, an LED display, a three-dimensional projection, an audio display, or a combination thereof. Furthermore, an RF sub-system/baseband processor 1010 may also be coupled to the processor 1002. The RF sub-system/baseband processor 1010 may include an antenna that is coupled to an RF receiver and to an RF transmitter (not shown). A communication port 1012, or more than one communication port 1012, may also be coupled to the processor 1002. The communication port 1012 may be adapted to be coupled to one or more peripheral devices 1014, such as a modem, a printer, a computer, a scanner, or a camera, or to a network, such as a local area network, remote area network, intranet, or the Internet, for example.

The processor 1002 may control the processor-based system 1000 by implementing software programs stored in the memory. The software programs may include an operating system, database software, drafting software, word processing software, media editing software, or media playing software, for example. The memory is operably coupled to the processor 1002 to store and facilitate execution of various programs. For example, the processor 1002 may be coupled to system memory 1016, which may include one or more of spin torque transfer magnetic random access memory (STT-MRAM), magnetic random access memory (MRAM), dynamic random access memory (DRAM), static random access memory (SRAM), racetrack memory, and other known memory types. The system memory 1016 may include volatile memory, non-volatile memory, or a combination thereof. The system memory 1016 is typically large so that it can store dynamically loaded applications and data. In some embodiments, the system memory 1016 may include semiconductor device structures, such as the semiconductor device structure 900 of FIG. 9, memory cells including any of magnetic cell cores 100-700 (FIGS. 1-7), or a combination thereof.

The processor 1002 may also be coupled to non-volatile memory 1018, which is not to suggest that system memory 1016 is necessarily volatile. The non-volatile memory 1018 may include one or more of STT-MRAM, MRAM, read-only memory (ROM) such as an EPROM, resistive read-only memory (RROM), and Flash memory to be used in conjunction with the system memory 1016. The size of the non-volatile memory 1018 is typically selected to be just large enough to store any necessary operating system, application programs, and fixed data. Additionally, the non-volatile memory 1018 may include a high capacity memory such as disk drive memory, such as a hybrid-drive including resistive memory or other types of non-volatile solid-state memory, for example. The non-volatile memory 1018 may include semiconductor device structures, such as the semiconductor device structure 900 of FIG. 9, memory cells including any of magnetic cell 100-700 (FIGS. 1-7), or a combination thereof.

The following example is presented to illustrate an embodiment of the present disclosure in more detail. This example is not to be construed as being exhaustive or exclusive as to the scope of this disclosure.

EXAMPLE

A partial magnetic cell core structure, without a magnetic contribution from a fixed region, was fabricated to evaluate the PMA strength of a free region fabricated according to an embodiment of the present disclosure. The partial magnetic cell core structure included a conductive seed region having a thickness of about 50 Å; an overlying dummy fixed region of CoFeB having a thickness of about 5 Å; an overlying nonmagnetic region of MgO having a thickness of about 12 Å; an overlying multi-material free region comprising a lower magnetic sub-region of CoFeB having a thickness of about 10 Å, an overlying spacer of Ta having a thickness of about 1.5 Å, and an overlying upper magnetic sub-region of CoFeB, with slightly different B concentration than the lower magnetic sub-region, having a thickness of about 6 Å; an overlying magnetic interface region of Fe having a thickness of about 4 Å; an overlying oxide capping region of MgO having a thickness of about 7 Å; and an overlying upper conductive capping region having a thickness of about 500 Å. This partial magnetic cell core structure exhibited a PMA strength (measured by H_(k) (Oe)) of 5,007 Oe, as indicated by data line 1200 of FIG. 11. This compares to a PMA strength of 2,992 Oe, as indicated by data line 1100 of FIG. 11, exhibited by the same structure lacking the magnetic interface region of Fe. Accordingly, the magnetic cell core structure with the magnetic interface region disposed over the free region, adjacent to the oxide capping region, exhibited a more than 50% increase in PMA strength compared to the same structure without the magnetic interface region.

While the present disclosure is susceptible to various modifications and alternative forms in implementation thereof, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure encompasses all modifications, combinations, equivalents, variations, and alternatives falling within the scope of the present disclosure as defined by the following appended claims and their legal equivalents. 

What is claimed is:
 1. A magnetoresistive structure, comprising: a free region configured to exhibit a switchable vertical magnetic orientation; a fixed region configured to exhibit a fixed vertical magnetic orientation; a nonmagnetic region between the free region and the fixed region; and a magnetic interface region spaced from the nonmagnetic region by one of the free region and the fixed region, wherein the magnetic interface region comprises one of a cobalt-iron based material and cobalt.
 2. The magnetoresistive structure of claim 1, wherein the magnetic interface region has a thickness less than about 10 Å.
 3. The magnetoresistive structure of claim 1, wherein the magnetic interface region is located directly between the nonmagnetic region and the free region.
 4. The magnetoresistive structure of claim 1, wherein the magnetic interface region is located between the free region and a capping region.
 5. The magnetoresistive structure of claim 1, wherein the magnetic interface region is disposed within the free region.
 6. The magnetoresistive structure of claim 1, further comprising another magnetic interface region disposed on a side of the free region.
 7. The magnetoresistive structure of claim 6, wherein the free region is disposed between the another magnetic interface region and the magnetic interface region.
 8. The magnetoresistive structure of claim 1, further comprising another magnetic interface region proximate the fixed region.
 9. A semiconductor device, comprising: a free region exhibiting a switchable magnetic orientation, the free region between an oxide region and another oxide region; a fixed region exhibiting a fixed magnetic vertical orientation on a side of the oxide region; a magnetic interface region between the oxide region and the another oxide region, the magnetic interface region having a thickness less than about 10 Å.
 10. The semiconductor device of claim 9, wherein the magnetic interface region directly contacts each of the oxide region and the free region.
 11. The semiconductor device of claim 9, wherein the magnetic interface region consists of iron.
 12. The semiconductor device of claim 9, wherein the oxide region comprises an oxide of magnesium, aluminum, or titanium.
 13. The semiconductor device of claim 9, further comprising another magnetic interface region contacting at least one of the free region and the fixed region.
 14. The semiconductor device of claim 9, wherein the free region comprises iron and at least one of cobalt and boron.
 15. The semiconductor device of claim 9, wherein an interface between the magnetic interface region and free region comprises iron from the magnetic interface region bonded to oxygen from the oxide region.
 16. A system, comprising: at least one magnetoresistive structure, the at least one magnetoresistive structure comprising: a free region configured to exhibit a switchable vertical magnetic orientation; an oxide region over the free region; a fixed region configured to exhibit a fixed vertical magnetic orientation over the oxide region; and a magnetic interface region spaced from the oxide region by one of the free region and the fixed region, wherein the magnetic interface region consists of iron; and a processor coupled to the at least one magnetoresistive structure.
 17. The system of claim 16, wherein the magnetic interface region has a thickness less than about 10 Å.
 18. The system of claim 16, further comprising another magnetic interface region in contact with at least one of the free region and the fixed region.
 19. A magnetoresistive structure, comprising: a free region configured to exhibit a switchable vertical magnetic orientation; a fixed region configured to exhibit a fixed vertical magnetic orientation; a nonmagnetic region between the free region and the fixed region; and a magnetic interface region spaced from the nonmagnetic region by one of the free region and the fixed region, wherein the magnetic interface region is located directly between the nonmagnetic region and the free region.
 20. A magnetoresistive structure, comprising: a free region configured to exhibit a switchable vertical magnetic orientation; a fixed region configured to exhibit a fixed vertical magnetic orientation; a nonmagnetic region between the free region and the fixed region; and a magnetic interface region spaced from the nonmagnetic region by one of the free region and the fixed region, wherein the magnetic interface region is located between the free region and a capping region.
 21. A magnetoresistive structure, comprising: a free region configured to exhibit a switchable vertical magnetic orientation; a fixed region configured to exhibit a fixed vertical magnetic orientation; a nonmagnetic region between the free region and the fixed region; and a magnetic interface region spaced from the nonmagnetic region by one of the free region and the fixed region, wherein the magnetic interface region is disposed within the free region.
 22. A magnetoresistive structure, comprising: a free region configured to exhibit a switchable vertical magnetic orientation; a fixed region configured to exhibit a fixed vertical magnetic orientation; a nonmagnetic region between the free region and the fixed region; and a magnetic interface region spaced from the nonmagnetic region by one of the free region and the fixed region, further comprising another magnetic interface region disposed on a side of the free region.
 23. A magnetoresistive structure, comprising: a free region configured to exhibit a switchable vertical magnetic orientation; a fixed region configured to exhibit a fixed vertical magnetic orientation; a nonmagnetic region between the free region and the fixed region; and a magnetic interface region spaced from the nonmagnetic region by one of the free region and the fixed region, further comprising another magnetic interface region proximate the fixed region.
 24. A system, comprising: at least one magnetoresistive structure, the at least one magnetoresistive structure comprising: a free region configured to exhibit a switchable vertical magnetic orientation; an oxide region over the free region; a fixed region configured to exhibit a fixed vertical magnetic orientation over the oxide region; a magnetic interface region spaced from the oxide region by one of the free region and the fixed region; and another magnetic interface region in contact with at least one of the free region and the fixed region; and a processor coupled to the at least one magnetoresistive structure. 